Fermented foods and probiotics for children. The importance of knowing their microbiological differences.

Breast milk provides microorganisms that colonize the gut and program the immune system to develop oral tolerance. Between the 6 months of exclusive breastfeeding and the recommended 2 years of prolonged breastfeeding, complementary feeding leads to a progressive reduction in the entry of live microorganisms into the gut ecosystem. This is because foods in general ‑unlike breast milk‑ are devoid of microorganisms or, if present, they are often inactivated during cooking. Fermented foods and probiotics could be a valuable nutritional strategy, as they would ensure the supply of live microorganisms in the face of a reduction or early cessation of breastfeeding. The terms "fermented foods" and "probiotics" are not synonymous. Microbiological identity, safety, and the existence of clinical efficacy studies supporting both are key to understand their differences and decide on an eventual dietary recommendation.